From Wikipedia. Original book source: Prof. Dr. Otto Wilhelm Thomé Flora von Deutschland, Österreich und der Schweiz 1885, Gera, Germany. Permission granted to use under GFDL by Kurt Stueber.
Near my house in south Edinburgh is the Braidburn Valley Park, said to be part of the very route that Robert Louis Stevenson followed when travelling to Edinburgh from his family’s summer home in Swanston. It’s quite a long walk but I suppose the young Robert would have used the time to ponder his next novel. He may have travelled on a donkey.
He would scarcely recognise the location today, with its large areas of neatly-mown grass and bright yellow swathes of planted daffodils. I go there to ponder quite often. I was there last week, checking up on the progress the Council are making with a wildflower meadow at the southern end. It’s too early for almost all the meadow species, but I did find the Cuckooflower (some call it Lady’s Smock, Latin name Cardamine pratensis) in full flower.
Cuckooflower in unmown grassland, Braidburn Valley Park, Edinburgh, 12th April 2023. The stem leaves are visible but the basal rosette of leaves is covered with the remains of last year’s grasses. Photo: John Grace.
It’s called Cuckooflower because it supposedly comes into flower when the first cuckoo is heard in mid-April. I have read that April 14th is known as Cuckoo Day but Britain has lost over three-quarters of its Cuckoo population since the 1980s and I rarely hear the bird’s song. Fortunately, the Cuckooflower itself has not declined. There has been no appreciable change in its distribution since the 1960s despite land drainage and herbicide use. It is found in almost every 10 km square of the UK and Ireland, and Michael Proctor listed it as one of the ‘ubiquitous species’ in his wonderful book Vegetation of Britain and Ireland.
Shakespeare wrote:
When daisies pied and violets blue
And lady-smocks all silver-white
And cuckoo-buds of yellow hue
Do paint the meadows with delight,
The cuckoo then, on every tree,
Mocks married men; for thus sings he:
“Cuckoo; Cuckoo, cuckoo!” O, word of fear,
Unpleasing to a married ear!
Love’s Labours Lost, William Shakespeare
Detail of the inflorescence. Flowers can be white, lilac or pink. Note the sequence of flowering – it starts at the base and progresses to the tip. There a 4 petals (6-18 mm long) and 6 stamens. The anthers are yellow. Photo: John Grace.
Cuckooflower is a native perennial, first recorded by Turner in 1562 and referred to in Gerard’s Herbal of 1597 as ‘Lady Smockes’. The name ‘Lady’s Smock’ was given presumably because the flower resembles the female apparel of ancient times. It belongs to the Cabbage and Mustard Family, the Brassicaceae. It grows in damp locations, typically reed-swamps and moist pastures but also by riversides. It prefers rather rich soils, mostly with a pH above 5, and it is sometimes found in partially shaded woodland habitats. In Britain, it is not limited by latitude or altitude – it is recorded from Scilly to Shetland and at sites from sea level to over 1000 metres in elevation.
Left: four leaves from the basal rosette; right: four leaves from the stem. The stem leaves usually have more leaflets than the basal leaves, and are narrower. Photo: John Grace.
Cardamine pratensis sprouts flowering shoots from an over-wintering basal rosette. As in all Cardamine species, the leaves are pinnate, but the leaflets of the stem-leaves are exceptionally slender. The seed pods are favourite food for the caterpillar of the Orange-tip Butterfly. One of the surprising features is that the basal leaves will often sprout new plants when they have contact with the soil. I knew nothing about this phenomenon until I started this blog and saw it mentioned in Clapham et al. (1987). It happens when the leaves fall to the ground in the late summer and autumn. Such clonal reproduction requires plenty of moisture but may even be the main method of regeneration at some sites. Salisbury (1965) wrote a whole paper about it, and called the phenomenon ‘leaf vivipary’. His technique was simple: he just floated the leaves or leaflets on water. His line drawings of the ‘birth’ of plantlets are very clear, and I would like to share them with our readers but alas, copyright and access to the original paper are restricted (as with many journals you have to be affiliated to a University or Research Institute even to view the results).
A similar method may also be useful to make new plants for small-scale wildlife meadows. Here are the instructions from an online conservation handbook:
“Fill a seed tray with moist compost. Place cuckooflower leaves flat on the surface of the moist compost and ensure that the compost and leaf make good contact. After three to four days small white roots will appear on the underside of the leaf. After two weeks the leaves have transformed into recognisable plants and should be transplanted into a pot to grow on”.
Detail of flowers. Note: flowers are protandrous: in the upper flower the stigma and style are not yet developed (very short) but the stamens are more developed; in the lower flower the stamens have completed their role of shedding pollen but the stigma and style are fully developed and presumably receptive. Salisbury (1965) pointed out that the flowers are self incompatible due to this protandry. Photo: Chris Jeffree.
Pollination is by bees, flies, moths and butterflies. Insects are attracted to nectar produced at the base of short stamens; the sugary solution is stored in pouches at the base of the sepals. The seeds vary greatly in size and are ejected from the capsule explosively, sometimes as far as 2 metres (Salisbury 1965). However, reproductive success is quite variable and some clones are virtually sterile, relying on vegetative spread.
Another unusual feature of the species is that the number of chromosomes is not constant. The situation was reviewed by Dale and Elkington (1974). In Sweden, Denmark, Poland and the Netherlands the chromosome count varies from 2n = 16 to 96. However, in Britain, the count is either 2n = 30 or 2n = 56 (Clapham et al. 1987). In Flora of the British Isles, Clapham at al. (1987) say the species represents ‘a very variable and taxonomically difficult polyploid complex with 8 as the basic chromosome number’. In Britain 2n = 56 is common and 2n = 30 is associated with drier habitats in S. England. But Dale and Elkington (1974) showed that there is a wide divergence in the appearance of plants that is quite unrelated to the number of chromosomes. In New Flora of the British Isles, Stace (2019) half-heartedly recognises three subspecies but says the species is ‘extremely variable and impossible to divide satisfactorily’. Meanwhile, Andrea Melichárková and colleagues have made a thorough survey of the cytology in Central Europe and propose several scenarios to account for the variation there (Melichárková et al. 2020). The authors point to possible hybridisation with related species. Species ranges would have become fragmented during glacial cycles and some populations would have survived in restricted glacial refugia, to be admixed with interbreeding when the ice sheets receded (Melichárková et al. 2020). But for me, the unanswered question is: if all this genetic shuffling occurred in Cardamine pratensis why didn’t it happen in many hundreds of other plant species?
Orange-tip butterfly (female) visiting a flower of garlic mustard, Alliaria petiolata. These butterflies are seen from the end of April to June, and visit flowers of various members of the Brassicaceae including Cardamine pratensis. The caterpillars feed on the developing seed pods. Note: only the male has an orange tip on its wings. Photo: Chris Jeffree.
Like some other members of the genus Cardamine, the species is recommended by foragers. The web site Plants for a Future says:
“Leaves and young shoots – raw or cooked. Rich in vitamins and minerals, especially vitamin C, but with a bitter and pungent flavour. The leaves and young shoots are harvested in the spring and taste rather like water cress. The leaves can be available early in the year and when used in small quantities make a very acceptable addition to salads. Flowers and flower buds – raw. A pungent cress-like flavour. The white flowers are very attractive, they make a pleasant nibble and also add a delicious flavour to salads”.
Global distribution on C. pratensis from GBIF. According to Plants of the World On-line the species is native to much of this range, but introduced to British Columbia and New Zealand.
The plant is often seen as merely a few more or less isolated individuals growing in damp grasslands. However, before launching this blog I returned once more to the Braidburn Valley Park and saw areas where masses of plants are growing together in a pale lilac haze. These displays are not the result of the Council’s attempt to recreate a wild meadow – they are neglected corners and damp patches immediately next to the Braid Burn itself. I presume the plants are the direct descendants of the landscape that Robert Louis Stevenson must have passed through on his way to the City, perhaps they are the very same clones.
References
Clapham AR, Tutin TG, Moore DM (1987) Flora of the British Isles, 3rd ed, Cambridge University Press, Cambridge.
Dale A and Elkington TT (1974) Variation within C. pratensis L. in England. Watsonia 10, 1-17.
Melichárková A et al. (2020) So Closely Related and Yet So Different: Strong Contrasts Between the Evolutionary Histories of Species of the Cardamine pratensis Polyploid Complex in Central Europe. Frontiers in Plant Science, Section Plant Systematics and Evolution, 11 | https://doi.org/10.3389/fpls.2020.588856
Salisbury EJ (1965) The reproduction of Cardamine pratensis L. and Cardamine palustris Peterman particularly in relation to their specialized foliar vivipary, and its deflexion of the constraints of natural selection. Proceedings of the Royal Society of London. Series B. Biological Sciences 163, 321 – 342.
Stace CA (2019) New Flora of the British Isles. C&A Floristics.
Noted added 16th May 2023
I place a detached leaves on wet kitchen paper and covered it all with a polythene bag. Salisbury was right – the leaves do indeed sprout offspring. Some of my leaves became infected by fungi and died but two out of five leaves sprouted. Here is the best one, now placed on peat-free compost.
©John Grace
Botany in Scotland 